Abstract 40: Transcriptome and DNA Methylation Changes in Patients with Subarachnoid Hemorrhage Undergoing Remote Ischemic Preconditioning

Abstract

Background: Remote ischemic conditioning (RIC) is a phenomenon by which brief periods of sublethal ischemia in one tissue confers protection from ischemia to distant tissues. We hypothesize that RIC triggers a cascade of integrated gene expression and methylation changes, leading to neuroprotection in subarachnoidal hemorrhage (SAH) patients. Our goal was to identify and compare changes in DNA methylation and gene expression profiles before and after RIC. Methods: Patients enrolled in a clinical trial of RIC after SAH, receiving RIC by limb cuff transient ischemia sessions. Fourteen SAH patients (64% female, mean age 51) underwent 3-4 RIC sessions and gave a blood sample before and after RIC, seven days apart. The transcriptome analysis of whole blood was performed using paired-end, 100-bp RNA-sequencing. We employed STAR and HTSeq to align and count reads; EdgeR to normalize the counts and detect differential expression (DE); and David to search for functional categories of the DE genes. Genome-wide DNA methylation profiles were assessed using reduced representation bisulfite sequencing (RRBS); Bismark with Bowtie to align the RRBS data, and the differential methylation analysis package (DMAP) to call the methylation status of CpG sites. Bedtools was used to overlap the DE genes with differentially methylated regions. Results: Of the 12,411 genes passing QC, 168 genes were differentially expressed after RIC (FDR<0.05). These genes were enriched for pathways involving mitosis and nuclear division (P50% after RIC in at least one individual. Of the 8,069 sites, 723 were differentially methylated (Bonferroni P<0.05). Our overlap analysis showed that 88 of the significantly altered methylation sites resided in 39 DE genes, including CEACAM8 and CRISP3, both implicated previously for stroke. Conclusions: Our data suggest that RIC alters expression of a specific set of genes involved in stroke via changes in regional DNA methylation. Further studies are warranted to replicate these pilot results.